Add Either[Throwable, T]-unwrapping methods

[adamw]

For situations when the left-side of an either should become a "panic" / bug.

Maybe: myEither.! - and then rename .ok() to myEither.? (when used within a bound)
Or: myEither.orThrow()

[adamw]

cc @lbialy maybe some bikeshedding? ;)

[adamw]

I'll go with .orThrow for now, but I'm not abandoning the idea of .? and .! ;)

[lbialy]

Oh, we're back to this discussion! I did not change my opinion on this and would definitely prefer .? and .! over .ok? and .orThrow :) It's a flow control structure, like send and ask in akka.